1. Field of the Invention
The present invention relates to a feed control device for controlling the relative speed of a tool and a workpiece in accordance with variation in loads.
2. Description of the Prior Art
The feed speed of a tool relative to a workpiece is generally determined in accordance with cutting conditions such as the material in use, the shape of the workpiece and the desired machining accuracy. However, even if the feed speed is initially set properly, the setting of the feed speed does not always remain proper since the cutting ability of the tool may decrease as the cutting operation on the workpiece proceeds when the shape, or surface roughness and hardness of the workpiece are not uniform. Particularly, problems arise when the workpiece is complicated in shape and is to be operated on non-continuously. Thus, defects and tool damage may occur because of great variations in load torque applied on the tool during the machining operation, lowering the machining accuracy and creating non-uniformity in finished workpieces.